Is that a mass brawl in Trafalgar Square? Feathers fly as world celebrates International Pillow Fight Day

It's a staple of childhood sleepovers, but thousands of people came out (pillow) fighting today as the world celebrated International Pillow Fight Day.

From Australia to Bangalore and Brazil, dozens of cities around the globe saw bedding brought into public squares for the fourth annual feather-fest.

London attracted more than 1,000 people to Trafalgar Square, with tens of thousands more joining in worldwide for the event which was started by The Urban Playground Movement.

Snow storm: Participants are almost obscured contents of pillows in Trafalgar Square, London

Playtime's over: Londoners throw their pillows in the air as the finishing horn is sounded

Flying high: The feathers swirl around Nelson's
Column in London, left, and cover the participants outside Zurich's
cathedral, right

The group's guide for would-be
organisers includes the advice not to use parks - both to avoid
littering and because 'most events in parks are boring' - and never to
ask permission.

'This may
change in the distant future if we witness some kind of crackdown
against free events and interventions, but in the meantime, it is very
unlikely that anybody will say yes,' they say.

'We
must also remind you: the "permit culture" we citizens witness in city
halls around the world is perhaps the single largest barrier to
experiencing the full richness of public life in the cities we live in.

'Do not ask for permission, public assembly is a human right.'

Feather fun: The feathers fly during the fight in Zurich

Prepare to sneeze: The pillow fight in central Sofia in Bulgaria

Clean-cut: But it's all a lot more
civilised at the Dr Sun Yat-sen Memorial Hall in Taipei, with a curious lack of feathers

The movement has a passionate mission to make such events in public 'a significant part of popular culture', using public spaces as 'urban living rooms' and replacing past-times such as watching television.

The UPM's guide ends: 'Imagine that in any large city, anywhere on the face of the Earth, there may some day be free, fun, massive public events like pillow fights, creative interventions, games and interactive art installations on every day of the year.

'Imagine that no matter where you went, you could find these events and the fun-loving clan that clings to them.

'Imagine that in the future, we will be united by our drive to live free, fun public lives! That is the era we dream of.'